The present invention relates to a cleaning device for use with transfer type electrostatic copying machines, and more particularly, to a cleaning device for use with transfer type electrostatic copying machines, wherein a wiping assembly is brought into slide contact with a photoreceptor during exposure to intercept residual toner particles on the photoreceptor.
The basic arrangement of transfer type electrostatic copying machines for forming a latent electrostatic image on the photoreceptor by exposure of a document, visualizing the latent electrostatic image by a toner, and transferring the toner image onto copying paper to provide a document image, has heretofore been well known, and today these types of copying machines are in wide use.
In such transfer type of electrostatic copying machine, since it takes time for the discharge by the corona discharger to rise and fall, the region of discharge onto the photoreceptor by the corona discharger prior to exposure is so arranged as to extend longer in the direction of travel of the photoreceptor than the exposure region. Since the discharge region is thus longer than the exposure region, the discharged region will include some unexposed portion, or untransferring portion in which a substantial amount of toner remains. Further, in cases where a large-sized document is copied using a small-sized copying paper sheet, the toner images will include some portion untransferred to the copying paper, or untransferred portion in which a substantial amount of toner remains. Thus, prior to the next copying operation, these residual toner particles should be removed to provide a copy having a clear reproduced image. To this end, a cleaning device is installed between the transfer region from which the toner image is transferred to the copying paper, and the charging region where the photoreceptor is uniformly charged by the corona discharger prior to exposure, so that the residual toner particles remaining subsequent to exposure are removed from the photoreceptor by the cleaning device.
Such cleaning devices which are well known include:
(1) A brush cleaning device (U.S. Pat. No. 2,832,977) of the type comprising one or more brushes whereby residual toner particles are separated from the photoreceptor and putting them into an air stream being discharged through a filter device:
(2) A web cleaning device (U.S. Pat. No. 3,186,838) of the type comprising a web of fibrous material adapted to pass over the photoreceptor surface to remove residual toner particles on the photoreceptor; and
(3) A blade cleaning device (U.S. Pat. No. 3,552,850) of the type comprising a pivotal head, a blade member fixed to said head, said blade member being adapted to be flexibly engaged with the photoreceptor surface to intercept residual toner particles, and a cam moving with the photoreceptor and adapted to keep the blade member away from the photoreceptor for a predetermined time to allow the intercepted residual toner particles to move together with the photoreceptor to the developing device, so that they can be reused.
Of these cleaning devices, the first two present problems that they occupy a large space, that they require a driving device, and that they are uneconomical because they cannot reuse residual toner. The last cleaning device eliminates these problems, and the corresponding U.S. Patent discloses that a plurality of blade members are arranged to intervals in the direction of travel of the photoreceptor.
However, U.S. Pat. No. 3,552,850 makes no disclosure whatsoever of setting individual slide contact pressures with which the blade members are to be pressed against the photoreceptor. As considered from the statement contained therein to the effect that different materials are used for different blade members to thereby ensure complete removal of the residual toner, it seems that the slide contact pressures for all blade members with respect to the photoreceptor are set so that they are the same.
With the cleaning device of the aforesaid arrangement, since residual toner particles are intercepted by the plurality of blade members, the intercepting effect is high, but the amounts intercepted by the blade members will differ and the blade members have to be made of different materials. The intercepting effect cannot be continuously controlled by using different materials, and it is very difficult to select optimum materials in accordance with the amounts to be intercepted. Thus, only rough selection would be possible. Therefore, the residual-toner intercepting effect would be insufficient or the slide contact pressures on the photoreceptor would be too high, causing premature wear of the photoreceptor.